Many attempts have been made to improve brewing cycle times and efficiencies and or to increase extraction rates. However, the art has not recognized the simple solution offered by the invention of contacting the roasted and ground coffee with steam for a short time period followed by extraction with water.
U.S. Pat. No. 4,389,924 to Hoesselbarth shows an automatic coffee maker which has a brewing unit which slides internally between brewing and rest positions. In the brewing position, brewing is accelerated by the use of a plunger which applies pressure directly to the brewing mixture to force it through a strainer. It would, however, be desirable to have a coffee making process which actually enhanced coffee flavor and aroma while increasing its rate of production.
In U.S. Pat. No. 4,583,449 to Dangel et al, there is disclosed a coffee maker which again makes coffee under pressure to speed brewing. To improve quality and simplify coffee maker construction, a through-flow heater is employed to carefully control water temperature and prevent it from being delivered to the roasted and ground coffee in a superheated state. The Dangel et al arrangement is intended to eliminate the need for a prior art water metering chamber which required preheating with steam. Thus, although prior art coffee brewers had steam capability and decreased brew cycle time by the use of pressure, it was not recognized that brief application of steam to the ground coffee could improve the quality of the brewed coffee.
In the preparation of high-solids-concentration extracts for spray drying to prepare dried "instant" coffee, steam treatment of roasted and ground coffee has been practiced to extract aromas. For example, in U.S. Pat. No. 4,707,368, Vogel et al use low-pressure, low-temperature steam for at least 15 minutes to extract aromatics which are later combined with the water extract for drying. There is no recognition that a short interval of steaming, without the preparation of a separate steam extract, would in any way enhance the quality of coffee brewed in typical pot or cup quantities for serving.
It is also known in industrial percolators for preparation of high solids extracts, to prewet the roasted and ground coffee prior to water extraction. This is noted by Sivetz and Desrosier, in Coffee Technology, The AVI Publishing Company, Inc., (1979) at pages 334-335. The authors also note at page 335 that, when beaker quantities of roast and ground coffee are added to boiling water, it takes about five minutes of boiling to wet the coffee particles. This time is not permissible for a modern home, office, restaurant or vending machine coffee brewer.